Light-emitting device

ABSTRACT

A light-emitting device includes a substrate, a light-emitting element disposed on the substrate, a light transmitting member disposed on the light-emitting element, and a covering body disposed on the substrate. The covering body covers a side surface of the light transmitting member and has an exposed upper surface. A particle group composed of a plurality of particles is dispersed in the covering body. The particle group includes a plurality of titanium oxide particles or zinc oxide particles dispersed in a vicinity of an upper surface of the covering body and each having a portion having a narrower band gap than in other portions of the particle.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a light-emitting device including alight-emitting element such as a light-emitting diode.

2. Background Art

Conventionally, there has been known a light-emitting device in which alight-emitting element that emits light having a predeterminedwavelength (emission color) and a wavelength converter that converts thewavelength of light from the light source are combined (for example,Japanese Patent Application Laid-Open No. 2010-219324).

SUMMARY OF THE INVENTION

In some cases, a light-emitting device is required not only to emithigh-intensity light (i.e., to have high output), but also to have aclear boundary between light and dark (i.e., to exhibit high contrast).In this case, the light-emitting device is required to be configured soas to emit high-output light from a specific region and not to emitlight from other regions.

The present invention has been made in view of the above-mentionedcircumstances, and an object thereof is to provide a light-emittingdevice achieving high output and high contrast with a simpleconfiguration.

The light-emitting device according to the present invention includes: asubstrate; a light-emitting element disposed on the substrate; a lighttransmitting member disposed on the light-emitting element; and acovering body that is disposed on the substrate, covers a side surfaceof the light transmitting member and has an upper surface exposed to theoutside, wherein the covering body has a particle group composed of aplurality of particles dispersed in the covering body, and the particlegroup includes a plurality of titanium oxide particles or zinc oxideparticles dispersed in a vicinity of the upper surface of the coveringbody and having a portion having a narrower band gap than that in otherportions in each particle.

The light-emitting device according to the present invention includes: asubstrate; a light-emitting element disposed on the substrate; and acovering body that is disposed on the substrate, covers a side surfaceof the light-emitting element and has an upper surface exposed to theoutside, wherein the covering body has a particle group composed of aplurality of particles dispersed in the covering body, and the particlegroup includes a plurality of titanium oxide particles or zinc oxideparticles dispersed in the vicinity of the upper surface of the coveringbody and having a portion having a narrower band gap than that in otherportions in each particle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of a light-emitting device accordingto a first embodiment.

FIG. 1B is a top view of the light-emitting device according to thefirst embodiment.

FIG. 1C is an enlarged cross-sectional view of the light-emitting deviceaccording to the first embodiment.

FIG. 1D is a cross-sectional view of particles in the covering body ofthe light-emitting device according to the first embodiment.

FIG. 2A is a diagram showing a producing method of the light-emittingdevice according to the first embodiment.

FIG. 2B is a diagram showing a producing method of the light-emittingdevice according to the first embodiment.

FIG. 2C is a diagram showing a producing method of the light-emittingdevice according to the first embodiment.

FIG. 3 is a diagram schematically showing a light path in thelight-emitting device according to the first embodiment.

FIG. 4 is a diagram showing light output from the light-emitting deviceaccording to the first embodiment.

FIG. 5A is a cross-sectional view of a light-emitting device accordingto a first modification of the first embodiment.

FIG. 5B is a cross-sectional view of a light-emitting device accordingto a second modification of the first embodiment.

FIG. 5C is a cross-sectional view of a light-emitting device accordingto a third modification of the first embodiment.

FIG. 5D is a cross-sectional view of a light-emitting device accordingto a fourth modification of the first embodiment.

FIG. 5E is a cross-sectional view of a light-emitting device accordingto a fifth modification of the first embodiment.

FIG. 6A is a cross-sectional view of a light-emitting device accordingto a second embodiment.

FIG. 6B is a top view of the light-emitting device according to thesecond embodiment.

FIG. 6C is an enlarged cross-sectional view of the light-emitting deviceaccording to the second embodiment.

FIG. 7A is a diagram showing light output from the light-emitting deviceaccording to the second embodiment.

FIG. 7B is a diagram showing light output from the light-emitting deviceaccording to the second embodiment.

FIG. 8A is a cross-sectional view of a light-emitting device accordingto a third embodiment.

FIG. 8B is a top view of the light-emitting device according to thethird embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail.

First Embodiment

FIG. 1A is a cross-sectional view of a light-emitting device 10according to a first embodiment. FIG. 1B is a schematic top view of thelight-emitting device 10. FIG. 1A is a cross-sectional view taken alongline V-V of FIG. 1B. FIG. 1C is an enlarged cross-sectional view showinga part A surrounded by a broken line in FIG. 1A in an enlarged manner.The configuration of the light-emitting device 10 will be described withreference to FIGS. 1A to 1C.

The light-emitting device 10 includes a substrate 11, a light-emittingelement 12 mounted on the substrate 11, a translucent member 13 disposedon the light-emitting element 12, and a light transmitting member 14disposed on the translucent member 13. In addition, the light-emittingdevice 10 has a frame body 15 arranged on the substrate 11 so as tosurround each of the light-emitting element 12, the translucent member13, and the light transmitting member 14 apart from each of thelight-emitting element 12, the translucent member 13, and the lighttransmitting member 14.

In addition, the light-emitting device 10 includes a covering body 16formed on the substrate 11 and covering the side surfaces (or the sidewalls) of the light-emitting element 12, the translucent member 13, andthe light transmitting member 14. The covering body 16 has an uppersurface S1 exposed to the outside. In addition, in the vicinity of theupper surface S1 of the covering body 16, there are disposed particlesthat absorb light that has entered the covering body 16 from the sidesurface of the light transmitting member 14 and is output to the outsidefrom the upper surface S1 of the covering body 16. The covering body 16will be described in greater detail below.

In the present embodiment, the substrate 11 is a mounting substratehaving a wiring for supplying power to the light-emitting element 12.The substrate 11 has a mounting surface of the light-emitting element12, and has a first wiring and a second wiring formed on the mountingsurface and electrically insulated from each other. In addition, thesubstrate 11 has a first external electrode and a second externalelectrode formed on a surface (back surface) opposite to the mountingsurface and electrically connected to the first wiring and the secondwiring, respectively. The light-emitting element 12 is mounted on thesubstrate 11 and connected to the wirings on the substrate 11.

The light-emitting element 12 is a semiconductor light-emitting elementsuch as a light-emitting diode, for example. In the present embodiment,the light-emitting element 12 includes a semiconductor layer (not shown)formed of a nitride-based semiconductor. The light-emitting element 12emits light in, for example, a blue region (wavelength of 420 to 470 nm)(hereinafter, sometimes referred to as blue light).

In this embodiment, the light-emitting element 12 includes a supportingsubstrate (for example, a silicon substrate), a semiconductor layerbonded to a first main surface of the supporting substrate, a firstelectrode formed on the first main surface of the supporting substrate,and a second electrode formed on a second main surface of the supportingsubstrate opposite to the first main surface and having a polaritydifferent from that of the first electrode. Note that the firstelectrode may be formed on the semiconductor layer bonded to the firstmain surface of the supporting substrate.

The second electrode of the light-emitting element 12 is electricallyconnected to the second wiring of the substrate 11 via a conductivebonding member. The first electrode of the light-emitting element 12 iselectrically connected to the first wiring of the substrate 11 via agold wire.

Note that the configuration of the light-emitting element 12 on thesubstrate 11 is not limited to this configuration. For example, as thelight-emitting element 12 having another configuration, may be mentioneda light-emitting element (hereinafter, referred to as a light-emittingelement 12A) having a growth substrate, a semiconductor layer grown onthe growth substrate, and a first electrode and a second electrodeformed on the semiconductor layer.

The light-emitting element 12A can be bonded to the substrate 11 bybonding the surface of the growth substrate on the opposite side to thesemiconductor layer to the mounting surface of the substrate 11, forexample, with a bonding member. The first electrode and the secondelectrode of the light-emitting element 12 can be bonded to the firstwiring and the second wiring of the substrate 11, respectively, via agold wire. When the light-emitting element 12A is mounted on thesubstrate 11, the growth substrate is disposed on the substrate 11, andthe semiconductor layer is disposed on the growth substrate.

As another configuration of the light-emitting element 12, may bementioned a case where the semiconductor layer of the light-emittingelement 12A is bonded to the mounting surface of the substrate 11(flip-chip bonding, hereinafter, referred to as a light-emitting element12B). In this case, the first electrode and the second electrode of thelight-emitting element 12B can be bonded to the first wiring and thesecond wiring of the substrate 11 by a conductive bonding member. Whenthe light-emitting element 12B is mounted on the substrate 11, thesemiconductor layer is disposed on the substrate 11, and the growthsubstrate is disposed on the semiconductor layer.

In the present embodiment, a case where the light-emitting element 12has a rectangular upper surface shape (regular square shape in thisembodiment) when viewed from a direction perpendicular to the mountingsurface of the light-emitting element 12 on the substrate 11 will bedescribed. However, the shape of the upper surface of the light-emittingelement 12 is not limited to a rectangular shape, and various shapessuch as a circular shape, an elliptical shape, and a long rectangularshape may be adopted. In this embodiment, the upper surface of thelight-emitting element 12 functions as a light extraction surface of thelight-emitting element 12.

The translucent member 13 is a member that transmits the light emittedfrom the light-emitting element 12, and is formed of, for example, amember that transmits at least visible light. For example, an epoxyresin, a silicone resin, a low melting point glass, or the like may beused as the material for the translucent member 13.

The translucent member 13 may include a wavelength converter, forexample, a phosphor, for converting the wavelength of the light emittedfrom the light-emitting element 12. For example, as the phosphor, agreen phosphor that converts blue light into green light, a yellowphosphor that converts blue light into yellow light, a red phosphor thatconverts blue light into red light, or the like can be used.

The configuration of the translucent member 13 is not limited to this.For example, the translucent member 13 may be composed of a nanoparticlesintered body of a metal oxide that transmits light emitted from thelight-emitting element 12 and light converted by a phosphor. Inaddition, the light-emitting device 10 does not need to have thetranslucent member 13.

The light transmitting member 14 is disposed on the upper surface of thetranslucent member 13. The light transmitting member 14 is a member thattransmits the light emitted from the light-emitting element 12 and/orthe light converted by the wavelength converter, and is formed of, forexample, a member that transmits at least visible light. For example, aglass plate, a sapphire plate, a YAG (Yttrium Aluminum Garnet) plate, orthe like can be used as the light transmitting member 14.

The light transmitting member 14 may include a wavelength converter, forexample, a phosphor, for converting the wavelength of the light emittedfrom the light-emitting element 12. For example, as the phosphor, agreen phosphor that converts blue light into green light, a yellowphosphor that converts blue light into yellow light, a red phosphor thatconverts blue light into red light, or the like can be used.

The configuration of the light transmitting member 14 is not limited tothis. For example, the light transmitting member 14 may be composed of ananoparticle sintered body of an acrylic resin, a silicone resin, afluorine resin, or a metal oxide that transmits the light emitted fromthe light-emitting element 12 and the light converted by the wavelengthconverter.

The upper surface of the light transmitting member 14 functions as alight extraction surface of the light-emitting device 10. In the presentembodiment, the upper surface of the light transmitting member 14 has ashape similar to that of the upper surface of the light-emitting element12, for example, a rectangular shape. However, the shape of the uppersurface of the light transmitting member 14 is not limited to arectangular shape, and may be a shape different from the shape of theupper surface of the light-emitting element 12. Further, for example,the side surface of the light transmitting member 14 may be formed in astepped shape, or may be inclined with respect to the upper surface.

The frame body 15 is disposed on the substrate 11 so as to surround eachof the light-emitting element 12, the light transmitting member 13, andthe light transmitting member 14 apart from each of the light-emittingelement 12, the light transmitting member 13, and the light transmittingmember 14. The frame body 15 may be disposed so as to surround the outerperiphery of the substrate 11. The frame body 15 may not be provided,and the outer side surface of the covering body 16 may be exposed.

In the present embodiment, the frame body 15 is formed integrally withthe substrate 11, and an alumina molded body (hereinafter, referred toas lamp house) having a concave portion for accommodating thelight-emitting element 12 is used as the substrate 11 and the frame body15.

The covering body 16 is formed on the substrate 11 in a region outsidethe light-emitting element 12, the translucent member 13, and the lighttransmitting member 14 and surrounded by the frame body 15. That is, inthe present embodiment, the frame body 15 defines the position of theouter edge (outer periphery) of the covering body 16 on the substrate11.

Hereinafter, the covering body 16 will be described in detail. Thecovering body 16 has the upper surface S1 exposed to the outside.Specifically, the covering body 16 is continuously disposed on thesubstrate 11 from the end of the upper surface (i.e., the lightextraction surface) of the light transmitting member 14 to the inner endof the upper surface (the surface opposite to the substrate 11) of theframe body 15. The covering body 16 is provided in an annular shape soas to surround the side surface of the light transmitting member 14.

The covering body 16 has a bottom surface in contact with the substrate11, an inner side surface in contact with the side surface of the lighttransmitting member 14, an outer side surface in contact with the innersurface of the frame body 15, and the upper surface S1 provided on theside opposite to the bottom surface and exposed to the outside.

In this embodiment, a case where the covering body 16 is in contact withthe entire side surface of the light transmitting member 14 will bedescribed. However, the covering body 16 may be in contact with only apart of the side surface of the light transmitting member 14. Forexample, the covering body 16 may cover only the partial side surface ofthe light transmitting member 14 (i.e., the upper region of the sidesurface of the light transmitting member 14) from the end portion of theupper surface (light extraction surface) of the light transmittingmember 14 toward the bottom surface of the light transmitting member 14(the surface through which light from the light-emitting element 12 andthe translucent member 13 enters).

In the present embodiment, a case where the covering body 16 is incontact with the entire inner surface of the frame body 15 will bedescribed. However, the covering body 16 may be in contact with only apart of the inner surface of the frame body 15. For example, thecovering body 16 may cover only a partial region from the upper end tothe lower end of the inner surface of the frame body 15 (that is, anupper region of the inner surface of the frame body 15).

Further, in the present embodiment, the upper surface of the frame body15 is configured to be higher in position from the substrate 11 than theupper surface of the light transmitting member 14. Therefore, thecovering body 16 is disposed in such a manner that the outer sidesurface thereof is higher than the inner side surface thereof. In thepresent embodiment, the covering body 16 includes a thermosetting resinas described later. Therefore, the upper surface S1 of the covering body16 has a shape slightly recessed toward the substrate 11 due to heatshrinkage after curing. Note that the upper surface of the frame body 15may be disposed at a position flush with the upper surface of the lighttransmitting member 14.

Next, the inner structure of the covering body 16 will be described withreference to FIGS. 1C and 1D. First, as shown in FIG. 1C, the coveringbody 16 has a particle group PT including a plurality of titanium oxideparticles (first, second and third titanium oxide particles P1, P2 andP3 are shown in FIG. 1C) dispersed in the covering body 16.

In this embodiment, the covering body 16 includes a medium (matrix) inwhich the particle group PT is dispersed. Examples of the medium includea thermosetting silicone resin and an epoxy resin. That is, the coveringbody 16 is formed of a resin body containing particles. In the presentembodiment, the resin body as the medium has a characteristic of capableof transmitting visible light.

In the present embodiment, the covering body 16 functions as a sealingbody for sealing the light-emitting element 12 and other functionalelements (such as a Zener diode for stabilizing the voltage applied tothe light-emitting element 12), wirings, and the like on the substrate11.

As shown in FIG. 1D, the respective first to third titanium oxideparticles P1 to P3 have particle bodies P10, P20, and P30, and coatingfilms P11, P21, and P31 covering the particle bodies P10, P20, and P30,respectively.

Specifically, in the present embodiment, the first titanium oxideparticle P1 has the particle body P10 (a portion made of titanium oxide)and the coating film P11 that covers the surface of the particle bodyP10 and protects the particle body P10. The coating film P11 is a filmformed of alumina, silica, or an organic substance such as polyol, forexample. Similarly, the second and third titanium oxide particles P2 andP3 have the particle bodies P20 and P30 and the coating films P21 andP31 covering the surfaces of the particle bodies P20 and P30,respectively.

Next, as shown in FIG. 1D, each of the first and third titanium oxideparticles P1 and P3 in the particle group PT has a portion NB having anarrower band gap than that in other portions in each particle (in eachof the particle bodies P10 and P30).

Also, as shown in FIG. 1C, in the present embodiment, the particle groupPT includes the first to third titanium oxide particles P1 to P3dispersed so that the density of the narrower band gap portion NB ineach particle is lowered from the upper surface S1 of the covering body16 toward the substrate 11. For the sake of clarity of the drawing, thefirst and third titanium oxide particles P1 and P3 are hatched in FIG.1C. In this embodiment, each of the titanium oxide particles P1 to P3 isformed of titanium dioxide (TiO₂) having a rutile-type crystallinestructure.

The density of the narrower band gap portion NB in each of the first tothird titanium oxide particles P1 to P3 is, for example, a ratio of aportion occupied by the narrower band gap portion NB in each particle,and is, for example, the area occupied by the narrower band gap portionNB on the surface of each of the particle bodies P10 to P30.

In the present embodiment, in the first titanium oxide particles P1dispersed in the region closest to the upper surface S1 of the particlegroup PT, the density of the portion NB having the narrower band gapthan that in other portions in the first titanium oxide particle P1 ishighest (the portion NB having the narrower band gap at the firstdensity).

For example, the narrower band gap portion NB of the first titaniumoxide particle P1 has a band gap energy smaller than the energy ofvisible light (in particular, the energy of the wavelength of visiblelight). For example, the narrower band gap portion NB of the firsttitanium oxide particle P1 has a band gap energy (e.g., about 1.5 eV)smaller than the energy of the light emitted from the light-emittingelement 12 (blue light in this embodiment) and the light emitted fromthe translucent member 13 (blue light and yellow light in thisembodiment).

In the second titanium oxide particles P2 dispersed in the regionclosest to the substrate 11 in the particle group PT, the density of thenarrow band gap portion NB in the second titanium oxide particle P2 islowest (the narrower band gap portion NB at the second density).

For example, the second titanium oxide particles P2 have almost nonarrower band gap portion NB, as shown in FIG. 1D. Thus, for example,the second titanium oxide particles P2 have a band gap energy greaterthan the energy of the emitted light from the light-emitting element 12in any part (almost entirely).

For example, when the second titanium oxide particle P2 has arutile-type crystal structure, the second titanium oxide particle P2 hasa band gap energy of 3.0 eV. When the second titanium oxide particle P2has an anatase-type crystal structure, the second titanium oxideparticle P2 has a band gap energy of 3.2 eV.

In the third titanium oxide particles P3 dispersed between the first andsecond titanium oxide particles P1 and P2 in the particle group PT, thenarrower band gap portion NB (a portion having a band gap energy of, forexample, 1.5 eV) in the third titanium oxide particle P3 is provided ata density (a third density (a density between the first density and thesecond density)) between the first titanium oxide particle P1 and thesecond titanium oxide particle P2.

Note that it is understood that the band gap of the crystal of titaniumoxide is narrowed by oxygen deficiency. More specifically, anintermediate level is formed between the valence band and the conductionband of titanium oxide due to oxygen deficiency. Here, the band gap isan energy gap between the intermediate level and the valence band or theconduction band. Therefore, for example, it is understood that thenarrower band gap portion NB in the first or third titanium oxideparticles P1 or P3 is a portion in which oxygen deficiency occurs in thecrystal of titanium oxide.

Here, the band gaps in the first to third titanium oxide particles P1 toP3 (i.e., local band gaps in the respective particles) will bedescribed. A crystal having a band gap has an optical characteristic ofabsorbing light having a wavelength whose energy is larger than the bandgap energy and transmitting light having a wavelength whose energy issmaller than the band gap energy.

In the present embodiment, the narrower band gap portion NB in each ofthe first and third titanium oxide particles P1 and P3 has a band gapenergy smaller than the band gap energy corresponding to the wavelengthof visible light. Accordingly, each of the first and third titaniumoxide particles P1 and P3 absorbs visible light by the narrower band gapportion NB. Therefore, in the present embodiment, the first and thirdtitanium oxide particles P1 and P3 exhibit black or gray because visiblelight is absorbed under observation using white visible light.

In this embodiment, since each of the second titanium oxide particles P2does not (substantially does not) have a narrower band gap portion NB,visible light is transmitted and scattered. Therefore, in thisembodiment, each of the second titanium oxide particles P2 exhibitswhite under observation using white visible light.

Further, in the present embodiment, when the regions in which the first,second, and third titanium oxide particles P1, P2, and P3 are dispersedin the covering body 16 are referred to as the first, second, and thirddispersion regions (or the first, second, and third particle layers)16A, 16B, and 16C, respectively, the first and third dispersion regions16A and 16C function as visible light absorption regions (hereinafter,simply referred to as absorption regions) AB that absorb visible light.On the other hand, the second dispersion region 16B functions as avisible light scattering reflection region (hereinafter, simply referredto as a scattering reflection region) SC for scattering and reflectingvisible light.

The first and third titanium oxide particles P1 and P3 are dispersedonly in a region near the upper surface S1 of the covering body 16. Forexample, the first and third titanium oxide particles P1 and P3 aredispersed only in a region within a depth range of 20 μm or less fromthe upper surface S1. Therefore, the covering body 16 functions as anabsorption region AB in the vicinity of the upper surface S1, andfunctions as a scattering reflection region SC in the inside thereof.

In the present embodiment, the first to third titanium oxide particlesP1 to P3 are dispersed in the covering body 16 (in the medium) with auniform dispersion density as a whole. However, the first to thirdtitanium oxide particles P1 to P3 may be dispersed so that thedispersion density (contained amount) gradually increases from the uppersurface S1 of the covering body 16 toward the substrate 11. For example,the dispersion density of the second titanium oxide particles P2 in thesecond dispersion region 16B may be higher than the dispersion densityof the first titanium oxide particles P1 in the first dispersion region16A.

The first, second, and third titanium oxide particles P1, P2, and P3have the coating films P11, P21, and P31, respectively, so that thefirst to third titanium oxide particles P1 to P3 have resistance toyellowing by ultraviolet rays (yellowing resistance) and weatherresistance.

Note that when resistance to yellowing by ultraviolet rays or weatherresistance is not required, the first to third titanium oxide particlesP1 to P3 may not have the coating films P11 to P31. For example, whenthe absorption region AB is formed in the vicinity of the upper surfaceS1 of the covering body 16, ultraviolet rays can be absorbed by theabsorption region AB. Therefore, in this case, the respective first tothird titanium oxide particles P1 to P3 do not need to have the coatingfilms P11 to P31.

FIG. 2A, FIG. 2B, and FIG. 2C are diagrams showing respective steps of aproducing method of the light-emitting device 10. Each of FIGS. 2A to 2Cis a cross-sectional view similar to that of FIG. 1A in each step. Themethod of producing the light-emitting device 10 will be described withreference to FIGS. 2A to 2C.

First, FIG. 2A shows the substrate 11 on which the light-emittingelement 12, the translucent member 13, the light transmitting member 14,the frame body 15, and a particle-containing resin 16P are formed. Inthis embodiment, first, a lamp house in which the frame body 15 isbonded to the substrate 11 is prepared (step 1). Next, thelight-emitting element 12 is disposed on the substrate 11 and bondedthereto (step 2). Next, the light transmitting member 14 (glass plate)is adhered onto the light-emitting element 12 via the translucent member13 containing a yellow phosphor (step 3).

Next, a silicone resin containing the same titanium oxide particles P0as the third titanium oxide particles P3 is filled as theparticle-containing resin 16P in the region between the lighttransmitting member 14 and the frame body 15 on the substrate 11 (step4). Then, the particle-containing resin 16P is heated and cured (step5). In this embodiment, rutile-type titanium dioxide having an averageparticle diameter of 250 nm and a band gap energy of 3.0 eV was used asthe titanium oxide particles P0. As the resin medium of theparticle-containing resin 16P, a silicone resin was used. Theconcentration of the titanium oxide particles P0 in theparticle-containing resin 16P was 16 wt %.

FIG. 2B is a diagram showing the upper surface of theparticle-containing resin 16P when the upper surface S0 of theparticle-containing resin 16P is being irradiated with the laser beam.After the particle-containing resin 16P has been cured, the uppersurface S0 of the particle-containing resin 16P exposed to the outsidein between the light-emitting element 12 and the frame body 15 isirradiated with the laser beam LB (step 6).

In this embodiment, a laser light source LS for emitting laser beam LBhaving a wavelength of 355 nm was prepared. Then, the laser beam LBhaving a beam diameter of φ45 μm and a power of 50 kW/cm² was irradiatedonto the upper surface S0 of the particle-containing resin 16P whilescanning the particle-containing resin 16P at a rate of 1000 mm/sec. Theenergy of light having a wavelength of 355 nm is about 3.5 eV, and theband gap energy of rutile-type titanium dioxide is 3.0 eV. Therefore,the energy of the laser beam LB is larger than the band gap energy ofthe titanium oxide particles P0. Therefore, the laser beam LB isabsorbed by the titanium oxide particles P0.

As a result, oxygen atoms are desorbed from the titanium oxide particlesP0 irradiated with the laser beam LB. In addition, by adjusting theirradiation intensity, the irradiation time, the focal position, and thelike of the laser beam LB, the laser beam LB is irradiated only to thetitanium oxide particles P0 in the vicinity of the upper surface S0.Therefore, the titanium oxide particles having the largest oxygendeficiency are generated in the vicinity of the upper surface S0 of theparticle-containing resin 16P, and the degree of the alteration (oxygendeficiency) of the titanium oxide particle P0 decreases as it is apartfrom the upper surface S0.

As a result, the titanium oxide particles P0 having much oxygendeficiency present in the vicinity of the upper surface S0 of theparticle-containing resin 16P become the first titanium oxide particlesP1 having a narrower band gap portion NB with a high density. Then, thetitanium oxide particles P0 apart from the upper surface S0 of theparticle-containing resin 16P become the third titanium oxide particlesP3 in which the narrower band gap portion NB is relatively small.

Also, when the titanium oxide particles P0 are apart from the uppersurface S0 by a predetermined distance (the distance at which the laserbeam LB is shielded by the titanium oxide particle), the titanium oxideparticles P0 existing there are not affected by laser irradiation andmaintain its characteristics. Therefore, the titanium oxide particles P0present in the vicinity of the substrate 11 become the second titaniumoxide particles P2 having almost no narrower band gap portion NB. Inthis manner, the covering body 16 including a plurality of titaniumoxide particles (particle group PT) dispersed such that the density ofthe portion NB having a narrower band gap than that in other portions ineach particle is gradually lowered, and the light-emitting device 10including the same can be produced by irradiating the laser beam (seeFIG. 2C).

In the step of irradiating the laser beam LB (step 6), it is preferableto adjust the laser light source LS and the laser beam LB so as not toalter other materials, for example, the medium of the covering body 16(for example, silicone resin), the translucent member 13, the lighttransmitting member 14, and the like. For example, by irradiating thelaser beam LB under the above-described conditions, only the titaniumoxide particles P0 can be altered while suppressing alteration of othermaterials.

The inventors of the present application have confirmed that the laserbeam LB under the conditions (and the power in the range of 25 to 75kW/cm²) does not alter the silicone resin as the medium of the coveringbody 16, the translucent member 13 and the phosphor in the translucentmember 13, and the glass plate as the light transmitting member 14. Inthis embodiment, a silicone resin having a transmittance of 60% or morewith respect to light having a wavelength of 355 nm was used as themedium of the covering body 16.

The method of producing the light-emitting device 10 is not limited tothis. For example, after the particle-containing resin 16P is appliedand left to stand for a predetermined time, the titanium oxide particlesP0 are precipitated by heating the particle-containing resin 16P. As aresult, it is also possible to form the covering body 16 in which thedispersion density of the titanium oxide particles P0 on the uppersurface S1 side is lowered.

FIG. 3 is a diagram schematically showing a light path in thelight-emitting device 10. First, almost all of the light emitted fromthe light-emitting element 12 passes through the translucent member 13and the light transmitting member 14 as in the light L1, and isextracted to the outside from the upper surface (light extractionsurface) of the light transmitting member 14.

Next, light entering the scattering reflection region SC of the coveringbody 16 from the side surface of the light transmitting member 14 (suchas light L2) is reflected by the scattering reflection region SC andreturns to the light transmitting member 14. Light such as the light L2is extracted from the upper surface of the light transmitting member 14to the outside.

On the other hand, light entering the absorption region AB of thecovering body 16 from the side surface of the light transmitting member14 (such as light L3) is absorbed by the absorption region AB. Inaddition, even when light such as the light L3 is not completelyabsorbed in the absorption region AB, the light is sufficientlyattenuated. Therefore, there is little light extracted from the uppersurface S1 of the covering body 16.

Therefore, when the light extraction surface of the light-emittingdevice 10 is observed, almost no light is extracted from a region otherthan the upper surface of the light transmitting member 14. Therefore,the bright and dark areas are clearly separated between the region ofthe light transmitting member 14 and the region other than the region,so that it is possible to obtain output light of high contrast. Inaddition, light incident on the covering body 16 from the outside, suchas stray light, is also absorbed or attenuated by the absorption regionAB of the covering body 16. Therefore, high contrast is maintained asthe light-emitting device 10.

In addition, the covering body 16 has high reflectivity for most of thelight incident on the covering body 16 from the sides of thelight-emitting element 12, the translucent member 13, and the lighttransmitting member 14, and has absorptivity for the light incident onthe covering body 16 from the outside. Therefore, the light-emittingdevice 10 can output light of high contrast without sacrificing adecrease in light output.

In addition, the absorption region AB of the covering body 16 can beeasily formed by simply adding the irradiation step (step 6) of thelaser beam LB. Therefore, it is possible to easily provide thelight-emitting device 10 achieving high output and high contrast.

FIG. 4 is a diagram showing a distribution of light output from thelight-emitting device 10. In FIG. 4, the horizontal axis represents theposition of the light-emitting device 10 along the line V-V in FIG. 1B,and the vertical axis represents the light output (the value obtained bynormalizing the luminance with the maximum value). In order to confirmthe effect of the light-emitting device 10, as a comparative example, alight-emitting device 100 in which the covering body 16 was formed of aresin body containing uniform titanium oxide particles was measured forits output in a similar manner as that for the light-emitting device 10.In FIG. 4, the output measurement result of the light-emitting device 10is shown by a solid line, and the output measurement result of thelight-emitting device 100 is shown by a broken line. Note that themaximum luminance of the light-emitting elements 10 and 100 was thesame.

As shown in FIG. 4, it can be understood that the output from a regionother than the region of the light transmitting member 14 (thelight-emitting element 12) in the light-emitting device 10 is greatlysuppressed as compared to the light-emitting device 100. On the otherhand, the output from the region of the light transmitting member 14 inthe light-emitting device 10 is approximately the same as that of thelight-emitting device 100. That is, it can be understood that thelight-emitting device 10 achieves high contrast without lowering theoutput.

In the present embodiment, the resin body as the dispersion medium ofthe particle group PT is integrally formed. That is, for example, eachof the first to third titanium oxide particles P1 to P3 in the coveringbody 16 is dispersed in the same medium. In addition, there is no mediumboundary between the first to third dispersion regions 16A to 16C.Therefore, even when the absorption region AB is provided, themechanical strength of the covering body 16 is maintained, and theoptical function is stabilized as described above. Thus, the coveringbody 16 and the light-emitting device 10 are of high quality and havelong life.

Further, in the present embodiment, the particle group PT has a uniformdispersion density as a whole in the covering body 16. Accordingly, eachof the first to third titanium oxide particles P1 to P3 is dispersed inthe covering body 16 at a density within the same degree as each other.Therefore, even in the case where the absorption region AB is provided,the thermal expansion coefficient of the covering body 16 as a whole ismade uniform, thereby maintaining the mechanical strength of thecovering body 16. Thus, the covering body 16 and the light-emittingdevice 10 are of high quality and have long life.

For example, as described above, when the dispersion density of thesecond titanium oxide particles P2 on the substrate 11 side is increasedand the dispersion density of the first titanium oxide particles P1 onthe upper surface S1 side is decreased, resin cracking of the uppersurface S1 of the covering body 16 can be prevented.

In the present embodiment, the covering body 16 includes a thermosettingepoxy resin or silicone resin having a refractive index in the range of1.4 to 1.55 as a resin medium. The particle group PT includes, forexample, anatase-type titanium oxide particles having a refractive indexof about 2.5 or rutile-type titanium oxide particles having a refractiveindex of about 2.7. In consideration of scattering light in the coveringbody 16, it is preferable that the particle group PT (in particular, thesecond titanium oxide particle P2) have a higher refractive index thanthat of the resin medium.

In consideration of obtaining good diffusion and reflectioncharacteristics, the particle diameter (average particle diameter) ofeach of the first to third titanium oxide particles P1 to P3 in theparticle group PT of the covering body 16 is preferably in the range of150 to 350 nm. Further, when the average particle diameter of the firstto third titanium oxide particles P1 to P3 is set within the range ofabout 1 to ¼ with respect to the wavelength of the light (visible light)that has entered the covering body 16 (for example, the wavelength inthe medium of the silicone resin), Mie scattering with a highbackscattering ratio can be generated, and extremely favorable diffusionand reflection characteristics can be achieved. When the averageparticle diameter of the particles in the particle group PT is adjustedin consideration of these factors, the reflectance in the scatteringreflection region SC can be enhanced. Also in the absorption region AB,light scattering causes light to be taken into particles with highprobability and absorbed, so that the absorptance can be increased.

The concentration of the particle group PT in the covering body 16 ispreferably in the range of 5 to 70 wt % in consideration of obtainingdesired light reflectivity and light absorption properties, and is morepreferably in the range of 8 to 30 wt % in consideration of ease ofproduction (ease of application of the particle-containing resin 16P)and production cost. Note that the above-described particle group PT andmedium configuration of the covering body 16 are merely examples.

Further, as shown in FIG. 1D, since the respective first to thirdtitanium oxide particles P1 to P3 have the coating films P11 to P31(i.e., the titanium oxide particles P0 used for forming each particlehave the coating film), oxygen deficiency can be effectively and stablygenerated on the surfaces of the particle bodies P10 to P30 by usinghigh-power laser having a wavelength of 355 nm in the step (step 6) ofirradiating the laser beam LB at the time of producing thelight-emitting device 10. In particular, when a coating film is providedfor the purpose of imparting yellowing resistance (resistance toultraviolet rays) to each particle, the absorption region AB can bestably formed only in a thin region of several μm from the upper surfaceS1 of the covering body 16.

When the particle diameter of the titanium oxide particles P0 issubstantially equal to the wavelength of the laser beam LB in theparticle-containing resin 16P, Mie scattering having a largebackscattering ratio is generated by the titanium oxide particles P0 inthe region in the particle-containing resin 16P. As a result, the laserbeam LB is scattered and reflected in the vicinity of the upper surfaceS0 of the particle-containing resin 16P, and as a result, the absorptionregion AB can be formed only in a thin region of several μm to 20 μm inthe vicinity of the upper surface S1 of the covering body 16.

When light at a wavelength whose energy is higher than the band gapenergy of the titanium oxide particles P0 in the particle-containingresin 16P is adopted as the laser beam LB, the laser beam LB can beabsorbed by the titanium oxide particles P0. Therefore, the absorptionregion AB can be formed only in a thin region of several μm to 20 μm inthe vicinity of the upper surface S1 of the covering body 16.

FIG. 5A is a cross-sectional view of a light-emitting device 10Aaccording to a first modification of the first embodiment. Thelight-emitting device 10A has the same configuration as that of thelight-emitting device 10 except for the configuration of a translucentmember 13A. In the present modification, the translucent member 13Acovers a part of the side surface of the light-emitting element 12. Thatis, the translucent member 13A is formed on the upper surface and theside surface of the light-emitting element 12. In the presentmodification, the covering body 16 is in contact with the light-emittingelement 12 in the lower region of the side surface of the light-emittingelement 12, and covers the light-emitting element 12 via the translucentmember 13A in the upper region thereof.

In the light-emitting device 10A, the covering body 16 has a portionthat is not in contact with the side surface of the light-emittingelement 12 at an upper region of the side surface of the light-emittingelement 12. When the covering body 16 is configured in this manner, thelight emitted from the side surface of the light-emitting element 12 canbe guided by the light transmitting member 13A to be incident on theouter edge portion of the light transmitting member 14. Accordingly, itis possible to increase the light extracted from the outer edge portionof the light transmitting member 14. Therefore, the light-emittingdevice 10A achieves high contrast.

FIG. 5B is a cross-sectional view of a light-emitting device 10Baccording to a second modification of the first embodiment. Thelight-emitting device 10B has the same configuration as those of thelight-emitting devices 10 and 10A except for the configuration of atranslucent member 13B. In the present modification, the translucentmember 13B covers the entire side surface of the light-emitting element12. That is, the translucent member 13B is in contact with the entireupper surface and the entire side surface of the light-emitting element12. In the present modification, the covering body 16 covers the sidesurface of the light-emitting element 12 with the translucent member 13Binterposed therebetween.

In the light-emitting device 10B, the covering body 16 is not completelyin contact with the side surface of the light-emitting element 12. Whenthe covering body 16 is configured in this manner, almost all of thelight emitted from the side surface of the light-emitting element 12 canbe made incident on the outer edge portion of the light transmittingmember 14 by the translucent member 13B. Accordingly, it is possible toincrease the light extracted from the outer edge portion of the lighttransmitting member 14. Therefore, the light-emitting device 10B emitslight with high contrast.

FIG. 5C is a cross-sectional view of a light-emitting device 10Caccording to a third modification of the first embodiment. Thelight-emitting device 10C has the same configuration as that of thelight-emitting device 10 except for the configuration of a translucentmember 13C and a light transmitting member 14A. In the presentmodification, the light transmitting member 14A has an upper surfacelarger than the upper surface of the light-emitting element 12. Thetranslucent member 13C is formed to extend from the side surface of thelight-emitting element 12 to the bottom surface of the lighttransmitting member 14A.

In the present modification, the light emitted from the light-emittingelement 12 enters the entire bottom surface of the light transmittingmember 14A via the translucent member 13C, and then is extracted fromthe upper surface of the light transmitting member 14A to the outside.The covering body 16 covers the side surface of the translucent member13C and the side surface of the light transmitting member 14A.Therefore, for example, the light emitted from the side surface of thelight-emitting element 12 can be made incident on the outer edge portionof the light transmitting member 14A by the translucent member 13C.Therefore, for example, it is possible to provide the light-emittingdevice 10C in which the size of the light extraction surface is enlargedwithout changing the size of the light-emitting element 12 and thereduction in contrast is suppressed.

FIG. 5D is a cross-sectional view of a light-emitting device 10Daccording to a fourth modification of the first embodiment. Thelight-emitting device 10D has the same configuration as that of thelight-emitting device 10 except for the configuration of a translucentmember 13D and a light transmitting member 14B. In the presentmodification, the light transmitting member 14B has an upper surfacesmaller than the upper surface of the light-emitting element 12. Thetranslucent member 13D is formed to extend from the upper surface of thelight-emitting element 12 to the side surface of the light transmittingmember 14B.

In the present modification, the light emitted from the light-emittingelement 12 enters the bottom surface and the side surface of the lighttransmitting member 14B via the translucent member 13D, and then isextracted from the upper surface of the light transmitting member 14B tothe outside. The covering body 16 covers the side surfaces of thelight-emitting element 12 and the translucent member 13D and the upperportion of the side surface of the light transmitting member 14B.Therefore, for example, it is possible to provide the light-emittingdevice 10D in which the size of the light extraction surface is reducedwithout changing the size of the light-emitting element 12 while theoutput and contrast are enhanced.

FIG. 5E is a cross-sectional view of a light-emitting device 10Eaccording to a fifth modification of the first embodiment. Thelight-emitting device 10E has the same configuration as that of thelight-emitting device 10 except that the translucent member 13 and thelight transmitting member 14 are not provided. The light-emitting device10E includes the substrate 11, the light-emitting element 12 disposed onthe substrate 11, and a covering body 17 covering the side surface ofthe light-emitting element 12. In the present modification, thelight-emitting device 10E has a frame body 15A having a heightcorresponding to the height (thickness) of the light-emitting element12. The covering body 17 is disposed in a region between the frame body15A and the light-emitting element 12 on the substrate 11.

The covering body 17 has the same configuration as that of the coveringbody 16 except that it covers the side surface of the light-emittingelement 12. The covering body 17 covers the side surface of thelight-emitting element 12 and has an upper surface S1 exposed to theoutside. Similarly to the covering body 16, the covering body 17 has aparticle group PT including a plurality of titanium oxide particles(e.g., first to third titanium oxide particles P1 to P3) dispersed in alayered manner such that the density of a portion NB having a narrowerband gap than that in other portions in each particle is lowered fromthe upper surface S1 toward the substrate 11.

In the present modification, the upper surface of the light-emittingelement 12 is exposed to the outside. In this case, the light emittedfrom the light-emitting element 12 is directly extracted to the outsidewithout passing through another medium. Also in the light-emittingdevice 10E, since the covering body 16 includes the particle group PT, alight-emitting device achieving high output and high contrast isprovided.

In the present embodiment, the case where the covering body 16 has theabsorption region AB and the scattering reflection region SC for visiblelight has been described. However, the configuration of the coveringbody 16 is not limited to this. For example, the light-emitting element12 may be configured to emit light in a band other than visible light.In this case, the absorption region AB and the scattering reflectionregion SC of the covering body 16 only need to have absorptivity andreflectivity, respectively, with respect to the light in the otherwavelength band and/or the light with another wavelength converted bythe wavelength converter.

In other words, for example, the particles in the covering body 16, theband gap configuration thereof, and the medium only need to be adjustedso as to have a region having light absorption and light reflectionproperties corresponding to the wavelength of the light emitted from thelight-emitting element 12 and the light emitted from the wavelengthconverter included in the translucent member 13 or the lighttransmitting member 14.

Further, in this case, in consideration of effectively providing theabsorption region AB and the scattering reflection region SC in thecovering body 16, for example, it is preferable that the titanium oxideparticles in the particle group PT have an average particle diametercorresponding to the wavelength in the covering body 16 of the lightemitted from the light-emitting element 12 and/or the light emitted fromthe wavelength converter included in the translucent member 13 or thelight transmitting member 14.

In consideration of maintaining mechanical strength of the covering body16, it is preferable that the covering body 16 has an integrally formedresin medium (e.g., silicone resin) in which a plurality of titaniumoxide particles of the particle group PT are dispersed.

In the present embodiment, the case where the particle group PT has thefirst to third titanium oxide particles P1 to P3 has been described, butthe configuration of the particle group PT is not limited to this. Forexample, the particle group PT may be composed of, for example, only twotypes of titanium oxide particles P1 and P2.

In this case, for example, the covering body 16 only needs to include aplurality of first titanium oxide particles P1 disposed at a positionclosest to the upper surface S1 and having a portion (portion NB) havinga narrower band gap than the energy of the light emitted from thelight-emitting element 12 at a high density, and a plurality of secondtitanium oxide particles P2 disposed closer to the substrate 11 than thefirst titanium oxide particles P1 and having a portion (portion NB)having a band gap narrower than the energy of the light emitted from thelight-emitting element 12 at a low density.

For example, the particle group PT only needs to include at least thefirst titanium oxide particles P1. That is, the particle group PT onlyneeds to include a plurality of titanium oxide particles (first titaniumoxide particles P1) dispersed in the vicinity of the upper surface S1 ofthe covering body 16 and having a portion NB having a narrower band gapthan that in other portions in each particle.

The particles constituting the absorption region AB and the scatteringreflection region SC in the particle group PT are not limited totitanium oxide particles. For example, zinc oxide (ZnO) has the sameproperties as those of titanium oxide. For example, zinc oxide has aband gap energy of 3.37 eV and transmits visible light. In addition,zinc oxide has a property of absorbing ultraviolet light having awavelength of 355 nm (for example, laser beam LB). Further, therefractive index of zinc oxide is 2.0, which is larger than therefractive index of the silicone resin (1.4 to 1.55). In addition, zincoxide forms a deep donor level due to oxygen deficiency and narrows theband gap (a portion corresponding to a portion NB having a narrower bandgap is formed), and has the property of absorbing visible light.

Therefore, as the particle group PT, for example, a metal oxide crystalsuch as a titanium oxide particle or a zinc oxide particle having aproperty of transmitting visible light in a crystal state without oxygendeficiency and absorbing visible light by oxygen deficiency can be used.For example, the first to third titanium oxide particles P1 to P3 may bereplaced with the particles of the metal oxide having such properties,or the particles of the metal oxide may be contained in the particlegroup PT in addition to the first to third titanium oxide particles P1to P3.

In addition to the titanium oxide particles or zinc oxide particles,particles that scatter light emitted from the light-emitting element 12and/or light emitted from the wavelength converter contained in thetranslucent member 13 or the light transmitting member 14 may be addedto the particle group PT. Examples of such particles include metalcarbides, metal oxides, and metal nitrides such as silicon carbide(SiC), silicon nitride (Si₂N₃), gallium nitride (GaN), aluminum nitride(AlN), and aluminum oxide (Al₂O₃).

That is, the particle group PT only needs to include a plurality ofparticles dispersed in the covering body 16. When the particle group PTincludes a plurality of particles including particles other than thetitanium oxide particles and the zinc oxide particles, the plurality ofparticles may be dispersed at a uniform density in the covering body 16or may be dispersed so as to gradually increase in density from theupper surface S1 toward the substrate 11. In addition, for example, allof the particles included in the particle group PT may be dispersed atthe above-described concentration.

In this embodiment, the case where the light-emitting device 10 includesone light-emitting element 12 has been described. However, thelight-emitting device 10 may include a plurality of light-emittingelements 12. Also in this case, for example, the covering body 16 havingthe particle group PT only needs to cover the side surface of the lighttransmitting member 14.

Thus, for example, the light-emitting device 10 includes the substrate11, the light-emitting element 12 disposed on the substrate 11, thelight transmitting member 14 disposed on the light-emitting element 12,and the covering body 16 that covers the side surface of the lighttransmitting member 14 on the substrate 11 and has the upper surface S1exposed to the outside.

The covering body 16 has the particle group PT composed of a pluralityof particles dispersed in the covering body 16. The particle group PTincludes a plurality of titanium oxide particles (first titanium oxideparticles P1) or zinc oxide particles dispersed in the vicinity of theupper surface S1 of the covering body 16 and having a portion NB havinga narrower band gap than that in other portions in each particle.Therefore, it is possible to provide the light-emitting device 10achieving high output and high contrast with a simple configuration.

For example, the light-emitting device 10E includes the substrate 11,the light-emitting element 12 disposed on the substrate 11, and thecovering body 17 that covers the side surface of the light-emittingelement 12 on the substrate 11 and has the upper surface S1 exposed tothe outside. The covering body 17 has the particle group PT composed ofa plurality of particles dispersed in the covering body 17. The particlegroup PT includes a plurality of titanium oxide particles (firsttitanium oxide particles P1) or zinc oxide particles dispersed in thevicinity of the upper surface S1 of the covering body 17 and having aportion NB having a narrower band gap than that in other portions ineach particle. Therefore, it is possible to provide the light-emittingdevice 10E achieving high output and high contrast with a simpleconfiguration.

Second Embodiment

FIG. 6A is a cross-sectional view of a light-emitting device 20according to a second embodiment. FIG. 6B is a top view of thelight-emitting device 20. FIG. 6A is a cross-sectional view taken alongline W-W in FIG. 6B. FIG. 6C is an enlarged cross-sectional view showinga part B surrounded by a broken line in FIG. 6A in an enlarged manner.

The light-emitting device 20 has the same configuration as that of thelight-emitting device 10 except for the configuration of a covering body21. In the light-emitting device 20, the covering body 21 covers theside surface of the light transmitting member 14 and has the uppersurface S1 exposed to the outside, similarly to the covering body 16.

In the present embodiment, the covering body 21 has a particle group PT1including a plurality of titanium oxide particles (first to thirdtitanium oxide particles P1, P2, and P3) dispersed so that the densityof the narrower band gap portion NB in each particle is lowered from apartial region of the upper surface S1 toward the substrate 11. In FIG.6C, the titanium oxide particles P1 and P3 are hatched.

In other words, the first titanium oxide particles P1 forming theabsorption region AB in the particle group PT1 are dispersed in a partof the upper surface S1 of the covering body 21. That is, the coveringbody 21 has the first dispersion region 21A only in a part of the uppersurface S1. In the other region of the upper surface S1, the coveringbody 21 has a second dispersion region 21B which is a region in whichonly the second titanium oxide particles P2 are uniformly dispersedtoward the substrate 11. The covering body 21 can be formed, forexample, by irradiating only a part of the upper surface S0 of theparticle-containing resin 16P with the laser beam LB.

In the present embodiment, the first titanium oxide particles P1 aredispersed in the covering body 21 so as to surround the lighttransmitting member 14 apart from the side surface of the lighttransmitting member 14 by a predetermined distance (distance D).Accordingly, the covering body 21 partially reflects and scatters thelight entering the covering body 21 from the side surface of the lighttransmitting member 14 (such as the light L3 in FIG. 3). Thelight-emitting device 20 has a suitable configuration when the highoutput is given priority among the high contrast and high power, forexample.

The balance between the output of the extracted light and the contrastcan be adjusted by adjusting the distance D (FIG. 6C) from the sidesurface of the light transmitting member 14 to the absorption region ABin the covering body 21, that is, the thickness of the scatteringreflection region SC in contact with the side surface of the lighttransmitting member 14 to the absorption region AB.

FIG. 7A is a diagram showing a distribution of light output from thelight-emitting device 20. The horizontal axis of FIG. 7A indicates theposition of the light-emitting device 20 along line W-W in FIG. 6B, andthe vertical axis indicates the light output (the value obtained bynormalizing the luminance with the maximum value). Also in FIG. 7A, themeasurement result of the light-emitting device 100 according to thecomparative examples is shown by a broken line and superimposed on themeasurement result of the light-emitting device 20. FIG. 7A shows themeasurement results of the light output from the light-emitting device20 when the distance D from the light transmitting member 14 to theabsorption region AB is 0.1 mm.

As shown in FIG. 7A, it can be understood that, also in thelight-emitting device 20, the output from the region other than theregion of the light-emitting element 12 (i.e., the light transmittingmember 14) is suppressed compared to the light-emitting device 100, andthe light having higher output is emitted from the region of thelight-emitting element 12. That is, it is understood that thelight-emitting device 20 is also a light-emitting device achieving highcontrast without lowering the output.

FIG. 7B shows the measurement result of the light output from thelight-emitting device 20 when the distance D from the light transmittingmember 14 to the absorption region AB is 0.2 mm. As shown in FIG. 7B,when the distance D is 0.2 mm, the light-emitting device 20 has the sameoutput value as that of the light-emitting device 100 up to the regionhaving the luminance of 1 when the luminance of the region of the lighttransmitting member 14 is 100.

That is, in the present embodiment, when the scattering reflectionregion SC is provided up to a position apart from the side surface ofthe light transmitting member 14 by a distance of 0.2 mm, light havingan intensity of 1/100 of that of the upper surface of the lighttransmitting member 14 is extracted to the outside from the region ofthe outer edge portion of the scattering reflection region SC.

In consideration of maintaining high contrast, it is preferable toprovide the scattering reflection region SC from the side surface of thelight transmitting member 14 to a position by a distance D at which theintensity becomes 1/100 or more of the light intensity on the uppersurface of the light transmitting member 14. In the present embodiment,it can be said that the distance D is preferably 0.2 mm or less. This isbecause light having an intensity of less than 1/100 is light having anintensity that does not deteriorate the contrast.

The distance D corresponds to a distance at which light can enter thecovering body 21 (scattering reflection region SC). The distance Ddepends on the dispersion density of the titanium oxide particles.Accordingly, it is preferable, for example, to measure the output fromthe light transmitting member 14 and its surrounding covering body 21 asdescribed above, and to provide a scattering reflection region SC to aposition closer to the side surface of the light transmitting member 14than the position where the output is 1/100 of the output from the uppersurface of the light transmitting member 14.

That is, it is preferable that the distance D be a distance from theside surface of the light transmitting member 14 to a position withinthe region of the upper surface S1 of the covering body 21 from whichlight of 1/100 or more of the maximum intensity of the light emittedfrom the light transmitting member 14 is emitted. In addition, it ispreferable that the covering body 21 have a plurality of titanium oxideparticles (e.g., first to third titanium oxide particles P1, P2, and P3)dispersed so that the density of the narrower band gap portion NB ineach particle is lowered in a region outside a position where lighthaving an intensity of 1/100 of the light output from the lighttransmitting member 14 is emitted (a position apart from the sidesurface of the light transmitting member 14 by a distance D).

Also in the present embodiment, the light-emitting device 20 does notneed to have the translucent member 13 and the light transmitting member14. In addition, the covering body 21 does not need to have thescattering reflection region SC over the entire circumference in thevicinity of the side surface of the light-emitting element 12. Forexample, the covering body 21 only needs to have a particle group PT1including a plurality of titanium oxides (first to third titanium oxideparticles P1, P2, and P3) dispersed in layers so that the density of thenarrower band gap portion NB in each particle is lowered from a portionof the upper surface S1 toward the substrate 11.

As described above, in this embodiment, for example, the first titaniumoxide particles P1 (titanium oxide particles disposed at the positionclosest to the upper surface S1 and having a portion (portion NB) havinga narrower band gap than the energy of the light emitted from thelight-emitting element 12 at a density higher than that of the otherparticles) of the covering body 21 are dispersed in the covering body 21so as to surround the side surface of the light transmitting member 14apart from the side surface of the light transmitting member 14 by apredetermined distance D. Accordingly, it is possible to provide thelight-emitting device 20 achieving high output and high contrast.

The covering body 21 has a plurality of second titanium oxide particlesP2 having a portion (portion NB) having a narrower band gap than theenergy of the emitted light from the light-emitting element 12 in aregion inside the first titanium oxide particles P1 (a region in contactwith the side surface of the light-emitting element 12 on the uppersurface S1) at a density lower than that of the first titanium oxideparticles P1. Therefore, the light-emitting device 20 has high output.

Third Embodiment

FIG. 8A is a cross-sectional view of a light-emitting device 30according to a third embodiment. FIG. 8B is a top view of thelight-emitting device 30. FIG. 8A is a cross-sectional view taken alongline X-X of FIG. 8B. The light-emitting device 30 has the sameconfiguration as that of the light-emitting device 10 except for theconfiguration of the covering body 31.

The covering body 31 has a plurality of concave portions 31R on theupper surface S1. In the present embodiment, as shown in FIG. 8B, eachof the concave portions 31R of the covering body 31 is formed in agroove shape so as to surround the periphery of the light-emittingelement 12, the translucent member 13, and the light transmitting member14. Each of the concave portions 31R has a cylindrical (imbricate) innerwall.

The covering body 31 can be formed, for example, by superimposing alaser beam LB (light having a wavelength in the ultraviolet region) onthe upper surface S0 of the particle-containing resin 16P andirradiating the laser beam LB a plurality of times. More specifically,by irradiating the laser beam LB having a wavelength of 355 nm and anoutput of 25 kW/cm² or more with a specified pattern, and irradiatingthe laser beam LB with the same pattern again, the silicone resin issuccessively sublimated and removed from the surface, and irradiatingtraces of the laser beam LB remain on the surface of the silicone resin.As a result, a groove corresponding to the beam diameter of the laserbeam LB and its moving direction is formed on the upper surface S0 ofthe particle-containing resin 16P. The resulting laser traces become theconcave portions 31R of the covering body 31.

Note that the concave portions 31R of the covering body 31 can be formednot only by irradiating the laser beam LB a plurality of times, but alsoby adjusting, for example, the output of the laser beam LB, the scanningspeed, and the like. The shape of the concave portion 31R is not limitedto the illustrated shape. For example, a convex portion may be formed onthe upper surface of the covering body 31, or a continuous irregularitymay be formed in the form of waves. The covering body 31 may have anupper surface S1 having various irregularities.

In this embodiment as well, the covering body 31 has the particle groupPT, having titanium oxide particles (first and third titanium oxideparticles P1 and P3) having a portion (portion NB) having a narrowerband gap than the energy of visible light, in the vicinity of the uppersurface S1 similarly to the covering body 16.

In the present embodiment, since the upper surface S1 of the coveringbody 31 has, for example, the repeatedly provided concave portions 31R,the area of the surface exposed to the outside is increased as comparedto, for example, a flat surface (for example, the upper surface S1 ofthe covering body 16). As a result, the surface area of the absorptionregion AB provided in the covering body 31 is increased. Therefore, thecovering body 31 absorbs light (such as the light L3 in FIG. 3) enteringthe covering body 31 from the side surface of the light transmittingmember 14 with high efficiency. Therefore, the light-emitting device 30has a suitable configuration when the contrast is given priority amongthe contrast and the output, for example.

In the present embodiment, the case where the concave portions 31R areformed over the entire upper surface S1 of the covering body 31 has beendescribed. However, the concave portions 31R may be formed only on apart of the upper surface S1 of the covering body 31. Also, the shapesof the concave portions 31R are not limited to the shapes shown in FIGS.8A and 8B. The covering body 31 only needs to have a concave portion 31Ron the upper surface S1.

This application is based on a Japanese Patent application No.2018-116751 which is hereby incorporated by reference.

What is claimed is:
 1. A light-emitting device comprising: a substrate;a light-emitting element disposed on said substrate; a lighttransmitting member disposed on said light-emitting element; and acovering body that is disposed on said substrate, that covers a sidesurface of said light transmitting member, and that has an upper surfaceexposed to an outside of said light transmitting member, wherein: saidcovering body has a particle group composed of a plurality of particlesdispersed in said covering body, said particle group includes aplurality of titanium oxide particles or zinc oxide particles dispersedin a vicinity of said upper surface of said covering body and eachhaving a portion having a narrower band gap than in other portions ofthe particle, and said particle group includes first titanium oxideparticles or zinc oxide particles disposed at a position closest to saidupper surface and having said portion having a narrower band gap at ahighest density, and second titanium oxide particles or zinc oxideparticles disposed closer to said substrate than said first titaniumoxide particles or zinc oxide particles and having said portion having anarrower band gap at a density lower than that of said first titaniumoxide particles or zinc oxide particles.
 2. The light-emitting deviceaccording to claim 1, wherein said covering body has an integrallyformed resin medium in which said plurality of particles are dispersed.3. The light-emitting device according to claim 1, wherein each of saidplurality of titanium oxide particles or zinc oxide particles comprisesa particle body and a coating film covering said particle body.
 4. Thelight-emitting device according to claim 1, wherein said first titaniumoxide particles or zinc oxide particles are dispersed in a region withina depth range of 20 μm or less from said upper surface of said coveringbody.
 5. The light-emitting device according to claim 1, wherein saidplurality of titanium oxide particles or zinc oxide particles aredispersed in said covering body so as to surround said side surface ofsaid light transmitting member apart from said side surface of saidlight transmitting member by a predetermined distance.
 6. Thelight-emitting device according to claim 5, wherein said predetermineddistance is a distance from said side surface of said light transmittingmember to a position within a region of said upper surface of saidcovering body from which light of 1/100 or more of a maximum intensityof light emitted from said light transmitting member is emitted.
 7. Thelight-emitting device according to claim 1, wherein said covering bodyhas irregularities on said upper surface.
 8. The light-emitting deviceaccording to claim 1, wherein each of said plurality of titanium oxideparticles or zinc oxide particles has an average particle diametercorresponding to a wavelength in said covering body of light emittedfrom said light emitting element.
 9. A light-emitting device comprising:a substrate; a light-emitting element disposed on said substrate; alight transmitting member disposed on said light-emitting element; and acovering body that is disposed on said substrate, that covers a sidesurface of said light transmitting member, and that has an upper surfaceexposed to an outside of said light transmitting member, wherein: saidcovering body has a particle group composed of a plurality of particlesdispersed in said covering body, said particle group includes aplurality of titanium oxide particles or zinc oxide particles dispersedin a vicinity of said upper surface of said covering body and eachhaving a portion having a narrower band gap than in other portions ofthe particle, and said plurality of particles in said particle group aredispersed in a range of 5 to 70 wt % in said covering body.
 10. Thelight-emitting device according to claim 9, wherein said plurality ofparticles in said particle group are dispersed at a uniform density insaid covering body.
 11. The light-emitting device according to claim 9,wherein said plurality of particles in said particle group are dispersedso as to gradually increase in density from said upper surface towardsaid substrate in said covering body.
 12. The light-emitting deviceaccording to claim 9, wherein said particle group includes saidplurality of titanium oxide particles or zinc oxide particles dispersedso that a density of a portion having a narrower band gap than that inother portions in each particle is lowered from said upper surface ofsaid covering body toward said substrate.
 13. The light-emitting deviceaccording to claim 9, The light-emitting device according to claim 1,wherein said covering body has an integrally formed resin medium inwhich said plurality of particles are dispersed.
 14. The light-emittingdevice according to claim 9, wherein said particle group includes firsttitanium oxide particles or zinc oxide particles disposed at a positionclosest to said upper surface and having said portion having a narrowerband gap at a highest density, and second titanium oxide particles orzinc oxide particles disposed closer to said substrate than said firsttitanium oxide particles or zinc oxide particles and having said portionhaving a narrower band gap at a density lower than that of said firsttitanium oxide particles or zinc oxide particles.
 15. The light-emittingdevice according to claim 14, wherein said first titanium oxideparticles or zinc oxide particles are dispersed in a region within adepth range of 20 μm or less from said upper surface of said coveringbody.
 16. The light-emitting device according to claim 9, wherein eachof said plurality of titanium oxide particles or zinc oxide particlescomprises a particle body and a coating film covering said particlebody.
 17. The light-emitting device according to claim 9, wherein saidplurality of titanium oxide particles or zinc oxide particles aredispersed in said covering body so as to surround said side surface ofsaid light transmitting member apart from said side surface of saidlight transmitting member by a predetermined distance.
 18. Alight-emitting device comprising: a substrate; a light-emitting elementdisposed on said substrate; and a covering body that is disposed on saidsubstrate, that covers a side surface of said light-emitting element,and that has an upper surface exposed to an outside of saidlight-emitting element, wherein: said covering body has a particle groupcomposed of a plurality of particles dispersed in said covering body,said particle group includes a plurality of titanium oxide particles orzinc oxide particles dispersed in a vicinity of said upper surface ofsaid covering body and each having a portion having a narrower band gapthan in other portions of the particle, and said particle group includesfirst titanium oxide particles or zinc oxide particles disposed at aposition closest to said upper surface and having said portion having anarrower band gap at a highest density, and second titanium oxideparticles or zinc oxide particles disposed closer to said substrate thansaid first titanium oxide particles or zinc oxide particles and havingsaid portion having a narrower band gap at a density lower than that ofsaid first titanium oxide particles or zinc oxide particles.
 19. Thelight-emitting device according to claim 18, wherein said first titaniumoxide particles or zinc oxide particles are dispersed in a region withina depth range of 20 μm or less from said upper surface of said coveringbody.
 20. The light-emitting device according to claim 18, wherein saidplurality of titanium oxide particles or zinc oxide particles aredispersed in said covering body so as to surround said side surface ofsaid light-emitting element apart from said side surface of saidlight-emitting element by a predetermined distance.
 21. A light-emittingdevice comprising: a substrate; a light-emitting element disposed onsaid substrate; and a covering body that is disposed on said substrate,that covers a side surface of said light-emitting element, and that hasan upper surface exposed to an outside of said light-emitting element,wherein: said covering body has a particle group composed of a pluralityof particles dispersed in said covering body, said particle groupincludes a plurality of titanium oxide particles or zinc oxide particlesdispersed in a vicinity of said upper surface of said covering body andeach having a portion having a narrower band gap than in other portionsof the particle, and said plurality of particles in said particle groupare dispersed in a range of 5 to 70 wt % in said covering body.
 22. Thelight-emitting device according to claim 21, wherein said plurality ofparticles in said particle group are dispersed at a uniform density insaid covering body.
 23. The light-emitting device according to claim 21,wherein said plurality of particles in said particle group are dispersedso as to gradually increase in density from said upper surface towardsaid substrate in said covering body.